Respiratory
Infections
Study
Outline on page 678-679
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Nasal
Cavity
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Oral
Cavity
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Tongue
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Epiglottis
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Trachea
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Larynx
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Tonsils
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Eustachian
Tube
Overview
Sinuses
and Nose
Respiratory Tree
Microbial
Diseases of the Respiratory Tract( and descriptions of the pathogens )
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Pharyngitis
–Inflammation of the mucous membranes of the throat or sore throat
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Laryngitis
– Streptococcus pyogenes or Streptococcus pneumoniae causes
swelling of the vocal cords- there is an inability to speak
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Tonsilitis
– Inflammation of the tonsils – swelling in the throat – fever -
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Sinusitis
– nasal sinuses have mucous membranes that become infected with a variety of
microorganisms . There is a heavy
discharge of mucous. The sinuses
can become blocked. The blockage
can cause pressure and pain. These
diseases may be self limiting – which means that the immune system overwhelms
the infectious agent.
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Epiglottitis
– the epiglottis is a flap like cartilaginous structure that separates the
respiratory tree from the digestive tract.
It is often infected by opprotunitstic organisms.
The vaccination for H. infleunze type b ( the Hib vaccine) has
significantly reduced the occurrence of epiglottitis in the population.
Streptococcal
Pharyngitis
q
Strep
throat – Group A, Beta hemolytic strep.
This group is essentially only Streptococcus pyogenes.
This bacteria is responsible for many infections of skin and soft
tissues.
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Beta
hemolytic streptococcus has been linked to impetigos well as endocarditis
( inflammation of the lining of the heart)
q
Group
A Beta hemolytic strep is resistant to the immune system and phagocytosis by the
white blood cells. The bacteria are
able to produce special enzymes called streptokinases that lyse fibrin clots and
streptolysins that are toxic to tissue cells, red blood cells, and protective
leukocytes.
Why
is Streptococcus pyogenes pathogenic
q
Capsule
– The capsule is composed of hyaluronic acid.
The presence of this capsule fools the immune system because the
hyaluronic acid outer covering is identical to human hyaluronic acid
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Fimbriae
– the fimbriae contain the virulence factor the M PROTEIN
The M proteins are antigenic and result in the formation of antibodies
against this protein. However, the
M proteins are variable from strep to strep so it is possible that individuals
become infected by different strep due to this factor.
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Steptococcus
releases exotoxins
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Streptococcus
releases cytolytic toxins and exoenzymes.
Streptolysin
O is a hemolysin that causes damage to human white blood cells
It
is strongly antigenic.
This
antigen can be used to test for recent infection by an ASO test
Hyaluronidase
– hydrolyzes the basic structure in human connective tissue
Streptokinase-
catalyzes the conversion of plaminogen to plasmin- this results in the lysis of
clots which hastens the spread of infection
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Originally
the presence of Group A Beta strep was verified by the culture of these
organisms on 5% sheep blood agar. The
presence of beta hemolysis indicated Steptococcus pyogenes or strep
throat. Rapid strep tests have
replaced the culture. The culture
could take 24 to 48 hours to identify the bacterium.
Now an agglutination diagnostic test is used to identify streprococcus.
Latex
particles coated with antibodies against group A streptococci + streptococcus
antigens yields a positive agglutination test.
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There
are individuals that are carriers for Beta streptococci
q
There
are other causes of throat infections – viruses
q
Positive
throat cultures are characterized by the inflammation of the throat and a fever.
q
The
lymph nodes in the neck and throat are enlarged and tender.
q
This
bacteria may also be accompanied by otitis media
q
There
are 80 serological types of streptococcus- that are linked to a variety of
diseases.
q
The
most common mode of transmission for strep throat is by respiratory secretions
Scarlet
Fever
q
When
S pyogenes causes a sore throat and produces an erythrogenic ( reddening toxin)
the resulting infection is called scarlet fever.
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When
the bacteria produces this toxin it has been lysogenized by a bacteriophage.
Refer
to the picture.
Lysogeny is an interaction between a bacteriophage
(
bacterial virus) and a bacteria
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The
toxin causes a skin rash with is due to a hypersensitivity to the toxin.
The tongue has a spotted, strawberry like appearance and then, as it
loses its upper membrane.
a.The
skin can peel off
b.It
is severely uncomfortable to eat
c.
It
is highly infectious
Additional
pathogenesis of strep in other organ systems
Impetigo
q
Childhood
disease
q
Usually
begins on the legs
q
It
can severe and extensive lesions on the face and limbs
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Impetigo
is treated with a topical agent such as mupirocin ro systemically with
penicillin.
GAS
q
Invasive
group A streptococcal ( GAS) disease
Common
during the first half of the century it has recently reemerged to become a
problem.
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Patients
have a deep local invasion without necrosis – this has been referred to as
“
Flesh eating bacteria”
Symptoms
may include fever, hypotension, and multi-organ involvement
Streptococcus
pneumonia
q
Gram
positive, nonmotilve encapsulated cocci.
Their shape is described as lancet shaped.
Their tendency to occur in pairs led to their identification as
diplococcus pneumonia.
q
This
is the most common cause of bacterial pneumonia and otitis media
The
risk of this disease is highest in babies, children, the elderly, and smokers.
Streptococcus
pneumonia causes alpha hemolysis in blood cultures
The capsule is antiphagocytic and antigenic. The bacteria are protected from the attacks of neutrophils
The
capsules are antigenic – however there are 85 distinctive types o capsules .
Some of these capsules are more antigenic than others.
The
occurrence of pneumonia is related to the increased level of secretions that are
difficult to clear from respiratory passageways as well as by secondary
infections of viruses.
q
Otitis
media is most frequently caused by pneumococcus as a primary infection and then
can be followed by Haemophilus influenzae.
The traditional treatment for this bacterium is a beta lactam
antibiotic- one that inhibits the growth of the cell wall
Diptheria
q
Upper
respiratory tract infection.
It used to be a killer.
q
Diptheria
is caused by Cornybacterium diptheriae, a gram positive non- endospore forming
rod. It
is pleomorphic which means that its shape is variable.
It has been described as a club shaped bacterium.
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This
infections begins with a sore throat and swollen lymph nodes
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The
diptheria toxoid
is the component of the DPT vaccine that causes the body to produce
antibodies against the diptheria toxi
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C.
diptheriae has adapted to an immunized population.
Many people today carry non pathogenic strain of bacteria
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The
characteristics of diptheria are to produce a membranous structure in the
airways that can block respiration.
This membrane that blocks the upper airways is formed by a fibrin like
clot, bacterial cells, and white blood cells
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These
bacteria can also produce an exotoxin when they are infected by a bacteriophage.
q
If
the toxin circulates in the blood stream it can enter tissue cells and affect
organs such as the heart and kidneys.
If the toxin affects the nerves paralysis can occur
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Laboratory
analysis requires both selective and differential media
q
Penicillin
and erythromycin are used to treat the bacterial infection
Mortality
Cutaneous
diptheria
The toxin can circulate through the blood stream
It is common in Native Americans and in tropical climate
Rhinoviruses
http://www.niaid.nih.gov/factsheets/cold.htm _ NAID
a. About 50% of colds are caused by a group of viruses called rhinoviruses
b. Corona viruses cause many other types of infections
c. Sneezing, secretions, congestion
d. Infections can spread to the sinuses or to the lower respiratory tract causing complications.
e. Rhinoviruses are highly infectious. It may not cause the presence of many viral particles to initiate the disease process.
f. There is no therapy( antibiotic) because colds are caused by viruses. It takes about a week for recovery.
Pertussis - Whooping Cough
a. Small obligate aerobic gram negative coccobacillus
b. The virulent or pathogenic strains have an outer capsule.
c. The bacteria attach to the psuedostratified epithelial cells in the respiratory tree that have cilia
d. The attachment of the bacterial cells to the cilia impedes their sweeping motion which tens to clear bacteria from the respiratory tree.
e. Tracheal cytotoxin- bacterial cytotoxin that destroys the cells lining the respiratory tract
f. The pertussis toxin can enter the blood stream and produce systemic effects
Stages
Catarrhal- common cold
Paroxysmal- coughing - the accumulation of mucous caused by the destruction of the ciliated cells, makes breathing difficult. The whooping sound is the result of gasping for air between coughs
Vaccinations
Lowered the incidence of this disease in the United Stats. In the 1950's the number of cases numbered 250,000. Today there are as many as several thousand, but very few deaths.
Vaccinations are acellular - which refers to the fact that the vaccine contains antigens from the bacterium rather than an attenuated strain
Tuberculosis
Tuberculosis Genome
a. Tubercuolosis is an infectious disease caused by Mycobacterium tuberculosis
b. The rods are slow growing and grow in clumps
c. They almost appear mold like in the media
d. These bacteria do not stain well with the Gram Stain . An Acid Fast Stain using a carbol fuschin dye cannot be decolorized with acid-alcohol and can be classified as acid-fast
e. The unusual nature of the cell wall which contains extra lipids provides extra resistance to dehydration or drying
TB
a. May be fought by natural immune defenses
Fluorescent micrographs of macrophages and TB bacterium
b. Individuals are more susceptible if they are exposed to additional pathogens, malnutrition, environmental stresses( air pollution)
c. Usually acquired by inhalation of the bacterium - that is the mode of entry for the bacterium into the body
Tuberculosis
and The Immune System
a. Tuberculosis reaching the alveoli of the lungs are ingested by macrophages
b. The bacteria multiply inside of the macrophages- This initiates a chemotactic response that attracts other immune cells. The release of cytokines by macrophages are not necessarily successful at killing the tuberculosis and can in fact cause lung damage.
c. The macrophages may die and form a tubercle. Inside the tubercle there may be bacteria that are capable of initiating a new infection after a period of dormancy.
d. The type of immune response is therefore cell mediated because the TB bacteria are actually within the macrophages.
TB TEST
a. A purified protein extract from the bacterium is inoculated cutaneously
b. If the person receiving the inoculation has been infected in the past - T cells will initiate a response- it is considered to be a hypersensitivity reaction and the skin becomes red and the site of inoculation swollen
c. A positive TB test in someone young is probably indicative of an active case
d. In older individuals the positive test may indicate a previous vaccination or infection. In this case the positive reaction will be followed up X- Rays
TB nodules in X-ray
BCG Vaccine
a. Live culture of Mycobacterium bovis, which has been made by attenuation- made avirulent by repeated passages through media
b. The vaccine is used for children in high risk situations and environments.
c. About 20,000 cases of tuberculosis are reported yearly. The mortality rate is decreasing.
d. One of the larges problems is the occurrence of TB in immigrants from Asia, the Philippines, and Mexico
Mycoplasma pneumoniae-
a. These bacteria do not have cells walls made of peptidoglycans
b. These may be confused with viral pneumonia
c. Found in individuals with weakened or compromised immune system
d. This is an atypical infection which responds to tetracylines
e. Primary atypical walking pneumonia
f. Sputum specimens are cultured. When they are grown on enriched media containing both yeast and horse serum, they produce colonies that have a " fried egg" appearance.
g. The colonies are quite small and the bacterium slow growing so that as long as two weeks may be required for the colonies to grow. It is therefore imperative to use more sophisticated means of diagnosis such as PCR which can yield results within hours.
Legionnaries's Disease
a. Received attention in 1976 at a meeting of the American Legion which was held in Philadelphia, Pennsylvania.
b. The symptoms of this infection by a rickettsial organismms, Legionella pneumophila,cause symptoms of extremely high fever and cough.
c. MOrphologically it is a gram - bacterium that can be traced to air conditioner ducts, humidifiers, and showers.
d. They are highly resistant to chlorine and heat
e. The diagnosis is made by culture on a charcoal-yeast media
Psittacosis( Ornithosis)
a. Is a term that describes the source of infection from parakeets and parrots
b. This disease may also be contracted from chickens, pigeons, and other birds
c. The symptoms of this disease include fever, high fever, headache and chills
d. The common mode of infection is from the dried particles from bird droppings
e. Tetracyclines are effective antibiotics in treating both animals and man.
Influenza Virus
a. Infects many individuals each year
b. characterized by fever, headache, and muscular aches
c. 10,000-20,000 individuals die yearly from this virus
a. Consists of eight separate RNA segments( RNA virus with a segmented genome)
b. Inner layer or protein covered by a lipid envelope( enveloped virus)
c. Two types of spikes on the exterior
hemagglutinin - _ H spikes are used for cellular recognition and infection
neuraminidase - N spikes allow the virus to exit the infected cell after it reproduces
Antigenic shifts - mutations or differences in the H or N spikes
Antigenic drifts- minor changes in the viral spikes
Histoplasmosis capsulatum - Fungal Respiratory Disease
Fungal infection of the respiratory tract. It has stages in which it resembles yeast and stages in which it resembles mold.
Humans acquire the spores if the conditions are correct( humidity) as well as the pH.
These conditions occur where there are high concentrations of bat and bird droppings Bats have a lower body temperature than birds, carry the fungus, excrete it in their feces, and infect soil
OHIO and Mississippi River Valleys
Coccidioidomycosis
Another fungal infection that can be found in the American Southwest
Spores are carried by the air( arthrospores). They are inhaled and the infection ensues
Very high incidence in California and Arizona - environmental disturbances exacerbate the level of infection in these areas
Amphotericin B and Imidazole drugs are used to treat this disease
Peumocystis pneumonia
Fungi or protozoan
Attacks immunosuppressed patients( HIV patients )
The microbes inhabit the lining of the aqlveoli
They form a thick-walled cysts